Brake operated transmission clutches with fully-resetting modulator-load-piston

ABSTRACT

A multi-functioning hydraulic transmission control circuit including interacting valve mechanism parts which, in response to a shift being called for in a clutch-cylinder-controlled multi-speed transmission, inaugurate a fill pressure flow to the clutch cylinders concerned, prior to the subsequent fluid pressure rise effected therein; thereafter, upon completion of the fill, the parts modulate pressure rise of the hydraulic clutch fluid from and at approximately actual clutch fill pressure up to, and remaining at, the final pressure of engagement. 
     These functions including full resetting of the parts at the beginning of each shift, and a lesser and a least gradual pressure rise afforded during respective second and third speed upshifts, are all accomplished by and among a pair of direction-selector and orificed-speed-selector valve spools connected to the transmission clutch cylinders to direct valve fluid output thereto selectively, and also 1st, dump valve, 2d, simulated clutch piston, 3d, load piston, 4th, modulator valve, and 5th, interacting spring parts collectively providing said directed valve fluid output, all in a valve bore common thereto, and arranged therein with the dump valve part confronted at one side by the simulated clutch piston part so as to define mutually therewith a differential pressure chamber in the bore, and confronted at the other side by a first side of the load piston part so as to define mutually with that first side a signal pressure chamber in the bore, and with an opposite side of the load piston part spacedly confronting the modulator valve part so that they mutually engage therebetween the interacting spring parts in the common bore.

This invention relates to hydraulic controls for smoothly effectingshifting of a vehicle transmission of the type in which the shiftingpower is provided by hydraulic pressure applied in the transmissionitself, i.e., to effect a smooth power-shift.

It more specifically relates to a multi-functioning hydraulictransmission control circuit including interacting valve mechanism partswhich, in response to a shift being called for in aclutch-cylinder-controlled multi-speed transmission, inaugurate a fillpressure flow to the clutch cylinders concerned, prior to the subsequentfluid pressure rise effected therein; thereafter, upon completion of thefill, the parts modulate pressure rise of the hydraulic clutch fluidfrom and at approximately actual fill pressure up to, and remaining at,the final pressure of engagement.

The above parts, which shift position either directly or indirectly inresponse to position changes made to a transmission shift lever by anoperator, comprise 1st speed selector and 2d direction selector valvespools connected to the transmission clutch cylinders to direct valvefluid output thereto selectively, and also 3d dump valve, 4th a loadpiston, 5th another piston, 6th a modulator valve, and 7th interactingspring parts collectively providing said directed valve fluid output,all in a bore common thereto, and arranged therein with the dump valvepart confronted at one side by the other piston part, 5th above, so asto define mutually therewith a differential pressure chamber in thebore, and confronted at the other side by a first side of the loadpiston part so as to define mutually with that first side a signalpressure chamber in the bore, and with an opposite side of the loadpiston part spacedly confronting the modulator valve part so that theymutually engage therebetween the interacting spring parts, 7th above, inthe common bore.

According to past transmission practices in tractors and other vehiclesin connection with controlled rate of rise valve assemblies eachincluding a modulator valve and an associated load piston therefore, thespeed and direction clutches provided in the transmission have beenoperated through the controlled rate of rise valve assembly to cushionclutch engagement. In tractor transmissions affording multi-speed rangesboth forward and reverse, it is neither necessary nor desirable that thepressure rise be as gradual in other transmission speed settings asidefrom the high torque, first speed which tends to engage jerkily, and atransmission works at a disadvantage without having a lesser and a leastgradual pressure rise afforded during respective second and third speedupshifts. And all the more it is a disadvantage that the rate of risevalve assembly is hydraulically spaced a long distance away from thetransmission controlled thereby so that the valve assembly in a senseoperates too remotely from, and altogether ignorantly of, the actualclutch fill pressure existing in the transmission itself. The latterdisadvantage manifests itself in the functioning of the modulator valveand load piston in some cases, with the load piston never fullyresetting itself, whereupon the subsequent fluid pressure rise starts ata point appreciably higher than actual clutch fill pressure in thetransmission itself and so no smooth, gradual shift results.

According to my invention, the foregoing disadvantages and drawbacks arematerially reduced in severity if not eliminated altogether, because thefunctions including full resetting of the parts at the beginning of eachshift, and a lesser and a least gradual pressure rise afforded duringrespective second and third speed upshifts, are all accomplished by andamong the novelly coacting parts hereinabove enumerated. One preferredway for such accomplishment resides in the present provision of asimulated clutch piston serving in the rate of rise valve assembly asthe other piston, 5th above, and in the present provision of an orificedbore housing progressively opened between the speed selector valvespool, 1st above, and the signal pressure chamber in the aforesaidcommon bore, all as will now be explained in detail. Features, objects,and advantages will either be specifically pointed out or becomeapparent when, for a better understanding of the invention, reference ismade to the following description taken in conjunction with theaccompanying drawings which show a preferred embodiment thereof and inwhich:

FIG. 1 is a schematic showing of a three speed forward, three speedreverse transmission and hydraulic power control system therefor, withthe rate of rise valve assembly of the present invention forming part ofthe control system shown;

FIGS. 2, 3, 4, and 5 are all enlarged cross sectional views of the rateof rise valve assembly of the invention, the same as appears as a detailin FIG. 1 and with the components shown in FIGS. 2-5 in variousoperating positions;

FIG. 6 is an isometric view of an hydraulic load piston appearing inlongitudinal cross section in each of the foregoing figures;

FIG. 7 is a graphical representation of a portion of pressure tracesdesirably and undesirably associated with the operation of the controlsystem foregoing; and

FIG. 8 is a graphical representation of complete pressure tracesassociated with the operation.

More particularly in the drawings, a reversible transmission 10controlled in accordance with my invention is shown in FIG. 1 havingthree speeds in the forward range and three speeds in the reverse range.The transmission 10 has hydraulically operated, clutch units controlledfirst by a piston and cylinder 1, and similarly by 2, 3, F, and R forpower shift operation. In one of the standard ways, the clutch unitscontrolling 1, 2, and 3 speeds are in the forward section of gearing,whereas the units controlling direction F-R are in the output section ofthe transmission 10.

Located forwardly of the transmission 10 are an engine driven hydraulicpump 12, and an engine driven torque converter 14 coupled to thetransmission 10 to provide torque-amplified input thereto.

Hydraulic drainage from various drains denoted D is collected in atransmission sump 16, from which it is drawn through a pump intake line18 into the inlet side of the hydraulic pump 12. From its pump outputside, the pump 12 discharges hydraulic fluid through an outlet line 20and a filter 22, thence into a pump pressure line 24 at pressure P.

Pump line pressure P enters a rate of rise valve assembly housing 26through a modulating pressure chamber conduit 28, through a modulatedbore core conduit 30, and through a rate of rise valve modulation borerestriction which is a large, fixed clutch-fill 32 forming a separatepart of a rate of rise valve assembly modulation bore 34 and feedingvalve output pressure P1 into a housing tee 36.

The tee 36 on the downstream side of the modulation bore restriction 32splits into lower and upper branches as viewed in FIG. 1. Hydraulicfluid under a valve modulated first output pressure P1 flows through thelower branch into a speed valve output connection 38. In the upperbranch, hydraulic fluid originally under pressure P1 is supplied to adirection valve output connection 40 at a valve modulated secondpressure P2 by way of a neutralizer valve bore 42 occupied at one end bya neutralizer valve spool 44.

In the valve housing 26, in a speed valve bore 46 interposed in thespeed valve output connection 38, a three-position speed valve spool 48is reciprocally positioned by the operator to selectively supply valvemodulated first output fluid to a set of individual speed lines 50leading to each one of the pistons and cylinders 1, 2, 3 of the clutchunits in the forward section of the transmission 10. Each line 50 is along one and, due to friction and restriction therein, the actual clutchpressure PA of the clutch units will be substantially less than thevalve modulated first output pressure P1.

Similarly, in a direction valve bore 52 interposed in the directionvalve output connection 40, a three-position direction valve spool 54 isreciprocally positioned by the operator to selectively supply valvemodulated second output fluid at pressure P2 to a pair of individualdirection lines 56 leading to pistons and cylinders F, R of the clutchunits in the output section of the transmission 10. Due to hydraulicfriction and restriction in each of the direction lines 56 which afforda long and somewhat tortuous path to flow of hydraulic fluid therein,actual pressure PA in the piston and cylinder F and in the piston andcylinder R will be substantially less than the pressure P2 in thedirection valve out put.

TORQUE CONVERTER -- FIG. 1

In the operation of the hydraulic system for torque amplification,hydraulic fluid keeps the torque converter 14 filled, being arrangedwith its supply of fluid provided by a rate-of-rise-pressure modulatingvalve 58 located in the right end of the rate-of-rise valve assemblymodulation bore 34, and with its back pressure maintained by a torqueconverter regulator valve spool 60 reciprocal in the left end of theneutralizer valve bore 42. More particularly, a back pressure land 62 onthe spring seated spool 60 is operatively located between a second coregroove 64 and a first core groove 66 connected to a converter outletline 68. As hydraulic pressure rises between the end of the spool 60 andthe left end of the bore 42 against which it is seated, the spool 60moves rightwardly in response to this increasing converter backpressure, and the intervening land 62 thereon opens andintercommunicates the first bore groove 66 and the second bore groove64, which latter discharges the excess hydraulic fluid therefrom througha cooler inlet line 70, an hydraulic torque converter cooler 72, acooler outlet line 74, and a housing oil gallery 76, thence into atransmission lube system L and ultimately into the transmission sump 16.

The rate-of-rise-pressure modulating valve 58 and a torque converterinlet line 78 provide a direct connection between the modulated borecore conduit 30 and the torque converter 14 on its inlet side. Moreparticularly, in the rate of rise valve assembly modulation bore 34,which bore is divided into the respective differential pressure chamber80, signal pressure chamber 82, spring chamber 84, and modulatingpressure chamber 86 as viewed in that order from left to right in FIG.2, the modulating valve 58 is of piston shape and arranged with thepiston end hydraulically separating the spring chamber and modulatingpressure chamber 84 and 86 in the bore 34.

During normal regulation, the valve 58 takes the regular intermediateopen position as shown in solid lines in FIGS. 1 and 2, having beenmoved by pressure in the modulating pressure chamber 86 to a point wherethe hydraulic pressure is exactly equal to and balanced by a partiallycompressed spring group 88 pressing against the inside of the valvepiston end. In that intermediate position shown, a regulating valve land90 maintains the pump pressure P in a bore core 92 by controlling flowof excess fluid into a bore core 94 thence to the torque converter (notshown in FIG. 2) through the torque converter inlet line 78. Additionalpressure encountered in the modulating pressure chamber 86, as due tostiff, very cold oil, will bring about progressive leftward openingmovement of the valve 58 causing cooperation between a bore core 96connected to drain D and dual function dump land 98 on the valve 58. Thedump land 98 has a valve edge with a first function whereby oil from thecores 92 and 94 will go directly to the bore core 96 and drain D, atleast until the oil warms up in the system. The dump land 98 also hasports 100 performing the second function, in all positions of the valve58, of continuously venting the spring chamber 84 to drain D by way ofthe core 96. A shoulder 102, formed on the valve 58 adjacent a valveseating spring 104, engages the fixed seat for spring 104 and limitsprogressive valve opening movement to a relatively short amount ofoverall valve travel.

An intermediate guide and seat 106 aligns inner ones of the springs ofthe spring group 88 which are connected thereby to act in tandem withinthe spring chamber 84.

The spring group 88 and associated parts within the rate of rise valveassembly modulation bore 34 form a rate of rise valve assembly generallyindicated at 108 and described in detail shortly.

SPEED VALVE -- FIG. 1

When the spool 48 in the speed valve bore 46 is detented at 110 in thefirst or 1 speed position as shown in solid lines, the speed lines 50 tothe respective piston and cylinder units 2 and 3 are connected by thespool 48 in readily discernible paths to drain D; at the same time fromthe output connection 38 in which the speed valve is located, the valvemodulated first output pressure P1 through a short conduit 112 isadmitted by an open spool land 114 into an individual speed line 50 andthe clutch piston and cylinder 1 so as to prepare the transmission 10for first speed drive.

Progressive inward movement of the speed valve spool 48 rightwardly soas to assume an intermediate or 2 position, causes the piston andcylinder 1 and 3 to be connected by the spool 48 to drain D; at the sametime valve modulated first output pressure P1 from the output connection38 and a core groove 116 is admitted by an open spool land 118 into theappropriate speed line 50 thence into piston and cylinder 2 to preparethe transmission 10 for second speed drive. Also at the same time, aspool land 120 uncovers the mouth of a first auxiliary passage 122interconnecting the short output conduit 112 and the signal pressurechamber 82 so as to provide a first supplement to the flow of fluid inthe latter for a reason later to be disclosed. That same spool land 120upon further depression of the spool 48 to extreme rightward positioncorresponding to speed 3, uncovers the mouth of a second auxiliarypassage 124 between the short ouput conduit 112 and the signal pressurechamber 82 to afford a second supplement to the flow of hydraulic fluidinto the latter.

When the spool 48 is fully depressed rightwardly for the speed 3condition, the clutch piston and cylinder units 1 and 2 are connected todrain D; at that time, the spool land 120 uncovers and leaves open acore groove 126 to pressure P1 in the short output conduit 112, so as topressurize the clutch piston and cylinder 3 and prepare the transmission10 for speed 3 condition.

DIRECTION VALVE -- FIG. 1

When the spool 54 in direction valve bore 52 is detented at 128registering at position F for forward drive as shown by solid lines, thevalve modulated second output pressure P2 which enters a core groove 130and direction valve bore 52 is directed by a spool land 132 into theappropriate individual direction line 56 and introduced by the latterinto the piston and cylinder F to complete forward drive in thetransmission. The individual line 56 to the clutch piston and cylinder Ris meantime connected by the spool 54 in a path leading through thehollow core 134 of the latter, past the detent 128, and thence to drainD in the transmission 10.

When the direction valve spool 54 is partway depressed into anintermediate position corresponding to N to neutralize the transmission10, the pressurized core groove 130 of direction valve bore 52 isblocked off by the spool land 132 and by an adjacent land 136, whereasboth direction lines 56 are connected to drain D in discernibledirection valve paths in FIG. 1. So the direction clutches aredisengaged and no drive is transmitted through the transmission 10.

Finally upon full depression of the spool 54 into its extreme positioncorresponding to the R condition of the transmission for reverse, thespool land 136 directs pressure P2 from the core groove 130 into a coregroove 138, whence it goes through the appropriate direction line 56into the clutch piston and cylinder R, completing the reverse paththrough the transmission 10. At the same time, the direction line 56 tothe clutch piston and cylinder F for forward drive is connected by thespool 54 in a path including the hollow core 134, past the detent 124,thence to drain D so as to keep the transmission forward drive inactive.

NEUTRALIZER -- FIG. 1

The neutralizer valve spool 44, which in a rightward position has acondition of repose as shown, and which has a controlled, shiftedposition to the left as viewed in FIG. 1, is under the electro-hydrauliccontrol of a brake operated, transmission neutralizer contacts component140, an electric neutralizer valve solenoid 142, and an hydraulicneutralizer valve component 144, all forming parts of a three-waycartridge solenoid valve assembly generally indicated at 146. The valveassembly 146 is in turn controlled by the vehicle brake pedal 148 in away automatically to neutralize the transmission 10 at all times duringwhich the vehicle brakes are applied.

During normal vehicle running conditions, the neutralizer valve spool 44occupies its rightward or repose position, and so do the brake pedal 148and valve assembly 146, all as shown in solid lines in FIG. 1. Duringsuch condition of repose, a spool groove 150 on valve spool 44, a spoolgroove 152 on valve component 144, and an interaction spring 154 betweenthe torque converter regulator valve spool 60 and the neutralizer valvespool 44 urging them to seat in opposite ends of the bore 42, areperforming as follows. The spool groove 150 completes an hydraulic pathbetween the housing tee 36 and direction output connection 40;therefore, the valve modulated first and second output pressures P1 andP2 are equal to one another, enabling the selected ones of the speed anddirection clutches to remain operative so that the transmission 10 staysengaged. The spool groove 152 completes an hydraulic path leading fromthe end of the bore 42 occupied by the corresponding end of theneutralizer valve spool 44, through a neutralizer valve line 156, thenceinto the groove 152, and a pair of series connected drain lines 158 and160 leading to drain D in transmission 10. So the unopposed spring 154holds the neutralizer spool 44 in its unshifted position of repose asshown in solid lines in FIG. 1, allowing the transmission 10 to continueto drive.

However, depression of the brake pedal 148 into the broken line positionshown, not only applies the vehicle brakes by conventional means, notshown, but also moves a switch arm counterclockwise as viewed in FIG. 1closing the transmission neutralizer contacts component 140 and settingthe transmission 10 in neutral. More particularly, contact closing inthe battery solenoid circuit illustrated electromagnetically causes thevalve solenoid component 142 to rise as viewed in FIG. 1 and to shiftupwardly the spool groove 152 therewith. Therefore, the modulatingpressure chamber 86 at pressure P is interconnected by way of a pressureline 162 with the spool groove 152, and at the same time the neutralizervalve line 156 is connected with the same spool groove 152, thuspressurizing that end of the valve bore 42 which is occupied by thecorresponding end of the neutralizer spool 44.

Accordingly, against the resistance of spring 154, the neutralizer spool44 is pressure actuated under pressure P into its shifted position, tothe left as viewed in FIG. 1; the neutralizer spool groove 150interconnects the direction valve output connection 40 and drain D,whereas pressure P1 from the housing tee 36 is blocked off by the mainportion of the neutralizer spool 44. Hence, the F-R direction clutchunits are disengaged, interrupting the transmission of power intransmission 10 always contemporaneously with brake application. So thevehicle brakes stop motion or arrest motion of the vehicle to the degreedesired, without having to overcome traction power of the engine aswell.

RATE OF RISE VALVE ASSEMBLY -- FIG. 3

Forming part of the rate of rise valve assembly 108, a load piston 164is controlled by hydraulic pressure of signal pressure chamber 82 and bymechanical pressure of the spring group 88 either to perform a resettingstroke in the bore 34 in the direction of an arrow 166, and to perform aloading, opposite reciprocal stroke to the right as viewed in FIG. 3.The piston 164 has a crown head which is formed with a shallow centralrecess 168 and which is subject to signal pressure S, and has the springgroup 88 seated inside the head so as to interact with the modulatingvalve 58 by reacting thereagainst and loading it for the desired rate ofrise modulation.

About the load piston 164, a uniplanar ring includes four spaced apartcontrol edges 170 that establish cooperation with two drain connectedbore ports 172, which ports are in the path of reciprocation of thepiston 164 and which are uncovered by the control edges 170 duringpiston movement to the right as viewed in FIG. 3.

Thus, travel of the load piston 164 during its loading stroke is limitedby the piston 164 venting the signal pressure S to drain immediately theports 172 are uncovered, and travel for resetting in the direction ofthe arrow 166 is limited as the piston 164 stops immediately uponcontact with, or in practice just short of, the dump valve 174 of anadjacent signal pressure control assembly 176.

DUMP VALVE -- FIG. 4

As viewed in its transient position adjacent signal pressure chamber 82in FIG. 4, the dump valve 174 will be appreciated to have primarycontrol over the emptying and filling of chamber 82. That is, leftwardmovement of the dump valve 174 opposite to the direction of an arrow 178will vent the signal pressure chamber 82 through a bore core 180 todrain, tending to empty the chamber. But movement of the dump valve 74in the direction of the arrow 178 causes a sealing edge 182 thereof toseal off an adjacent land 184 in the bore 34 and allow a constantdifferential, constant flow, timing orifice 186 fixed in the center ofthe dump valve 174 to fill the signal pressure chamber 82. The dumpvalve cavity pressure C within the differential pressure chamber 80causes essentially one way flow through the fixed orifice 186.

Within the dump valve cavity, a sleeve 188 is fixed and provides theseat for a light spring 190 urging the dump valve 174 to its sealedclosed position in the direction of the arrow 178. The head of the valve174 incoporates a pressure equalizing groove formation 192 to keep thevalve centered and free from binding.

SIMULATED CLUTCH FILL PISTON -- FIG. 5

Within the fixed sleeve 188 of the signal pressure control assembly 176,a simulated clutch fill piston 194 is reciprocally mounted to moverightwardly in the direction of an arrow 196 to an extreme positionlimited by a cross pin 198 fixed in the rate of rise valve assemblyhousing 26, or to move leftwardly opposite to the arrow's direction andbottom itself against the adjacent portion of the housing 26.

The dump valve 174 is in sole control of directing fluid to fill and toempty the piston cavity 200 of piston 194. In the valve-closed positionof the dump valve 174 as shown in FIG. 5, a dump valve land 202 divertsvalve cavity pressure C from the differential chamber 80 through a borecore 204 leading to the back of the piston, thence into a passage 206and the piston cavity 200. Pressure is thus equalized across the piston194 enabling a light spring 208 inside the head of the piston to movethe latter on a complete resetting stroke in the direction of the arrow196. But when the dump valve 174 is in the dump position to the left ofthe position shown in FIG. 5, the land 202 vents the bore core 204through the bore core 180 to drain D, enabling the valve cavity pressureC of the differential pressure chamber 80 to overcome the light spring208 and force the piston 194 leftwardly as viewed in FIG. 5 on acomplete control stroke.

STEADY STATE CLUTCH ENGAGEMENT -- FIG. 2

C is equal to P1 is equal to P is 30 psi greater than pressure S,according to this dynamic equilibrium condition as shown here. Thecondition can be accurately mechanically set, in view of the springchamber 84 always being maintained in drain pressure condition, in viewof the flow through the rate of rise valve modulation bore restrictionor clutch fill orifice 32 being inconsequential when the clutches arefully engaged, and in view of the strategic placement of the springgroup 88 in the spring chamber and of the valve seating spring 104engaging the head of the rate of rise pressure modulating valve 58.

More particularly, in spite of smallness or the magnitude of flow in thedirection of the arrow through the restrictive timing orifice 186, thespring group 88 is precisely calibrated so that the active one of thefour control edges 170 will restrict outflow from the bore ports 172constituting drain holes to the same restricted rate, thus maintainingthe signal pressure S in chamber 82 at a constant regulated value, e.g.,270 psi. On the other hand, the valve seating spring 104 which isprecalibrated to a moderate value, such as the equivalent to 30 psi,will act in conjunction with the same spring group 88 having theequivalent of 270 psi pressure, to cause rate of rise pressuremodulating valve 58 to regulate by means of the valve land 90 thereonwith the total of 300 psi as the pressure P. Because as noted, P equalsP1 equals C, cavity pressure C in the differential chamber 80 willmaintain constant flow through the restricted fixed orifice 186 creatingthe 30 psi pressure drop consistent with the signal pressure S remainingat 270 psi.

The restrictive flow through the timing orifice 186 making its way outthe drain holes 172 plus the regular leakage in the selected clutch ofeach of the two clutch groups totals a relatively minor flow in terms ofthe clutch fill orifice 32 which generates a barely perceptible pressuredrop thereacross.

DUMP, INITIATING CLUTCH FILL -- FIG. 3

Fill time is so comparatively short in a shift cycle of thetransmission, that the problem is to reduce the dump valve cavitypressure C to a low point and in turn reduce the signal pressure S to alow point, such that the resetting load piston 164 moving in thedirection of the arrow 166 will be able fully to complete the resettingstroke before the fill portion of the clutch cycle can elapse. Thecomplicating aspect is that the pressure P1 of the valve output fluidwhich restrictively enters the dump valve cavity of which the pressureis C, must have a value of about 50 psi in order that, at the clutchitself, the effective pressure PA actually filling the clutch will beabout 20 psi. The tendency which therefore must be overcome is that thesignal pressure S will be too high when, preferably, it should be at orabout actual clutch fill pressure of 20 psi so as not unduly to opposefull reset of the load piston 164.

In approaching the present solution to the problem, let it be assumed ashift is being made with the transmission in first gear, and with achange in the direction clutches, e.g., from reverse R to forward F.Hence, the clutch piston and cylinder unit 1 will remain filled whereasthe clutch piston and cylinder unit F, not shown, will be empty andrequire complete filling. So all pressures in the system will dropdrastically because 20 psi actual clutch filling pressure is all that isrequired by the empty clutch piston and cylinder.

P is 10 psi greater than P1, is equal to P2, is 30 psi greater than S,is equal to C, is equal to actual clutch fill pressure PA (20 psi),according to the condition illustrated in this figure, with substantialflow through the large clutch fill orifice 32 creating a 10 psi droptherein because of the large volume of fluid temporarily goingtherethrough. A glance for the moment back at FIG. 1 and specifically atextended-length direction lines 56 will make it clear how fluid fromdirection valve spool 54 can drop 30 psi in pressure from P2 to theactual clutch pressure PA by the time it arrives at the selected clutchpiston and cylinder unit F.

The cascading drops in pressures PA, P2 and P1 due to empty piston andcylinder unit F on the line, and the drop in cavity pressure C due tothe precipitous drop of the valve modulated first output pressure P1,results in the residual 270 psi signal pressure S forcing the dump valvepiston 174 in the direction of the arrow 210 in FIG. 3 to the openposition causing two coordinated actions. First, the dump valve controledge 182 opens a path from signal pressure chamber 82 through bore core180 to drain D, reducing the signal pressure S to about 20 psi andallowing the load piston 164 under force of the spring group 88 to resetleftwardly in the direction of the arrow 166. Second, the dump valveland 202 vents fluid from the piston cavity 200 and the passage 206 fromthe back of the piston and bore core 204, through the bore core 180thence to drain D, enabling the approximately 20 psi cavity pressure Cto move the piston 194 in the leftward direction of the arrow 210against the minor resistance of the light piston spring 208.

So, contemporaneously with only the major first part of clutch fill, thesimulated clutch fill piston 194 makes a complete control stroke,enlarging the volume of the differential pressure chamber 80 at a fairlysteady rate against the opposition of the light spring 208 within thepiston head. At the same time fluid flow in the valve output connection38 at pressure P1 will restrictedly enter the differential pressurechamber 80, through appropriate admission means such as through areduced diameter hole 212 at the back of the dump valve 174, at reducedpressure. As a matter of practice, the cavity pressure C and the signalpressure S are substantially equal, with the latter pressure S (about 20psi) being only enough the higher of the two by the minor amountnecessary to keep the light spring 190 under compression and the dumpvalve 174 hydraulically held open throughout clutch fill. Flow at thistime through the timing orifice 186 is essentially zero.

Under the favorable clutch fill condition just outlined, the load piston164 will execute a complete resetting stroke contemporaneously with onlythe major first portion of clutch fill time, balanced against theexisting 20 psi signal pressure, the spring group 88 will relax exceptto the extent of transmitting an equivalent of 20 psi pressure, and themodulating valve 58 will be modulating the line pressure P in the rangeof 50 or 60 psi or so.

END OF FILL -- FIG. 4

Toward the end of clutch fill, the load piston 164 will have taken itsextreme position of full reset as indicated, and the simulated clutchpiston 194 in this figure is shown to have completed its control stroke.Inherent with the ending of clutch fill, flow through the clutch fillorifice 32, not shown, drastically reduces, the pressure dropthereacross disappears, and the valve modulated first output pressure P1and second output pressure P2 increase about 10 psi immediately to thepump line pressure of, say, 60 psi. The dynamically balanced dump valve174 becomes hydraulically unbalanced because of the pressure rise in theP1 connected hole 212 leading to the back of the valve 174. The valve174 therefore shifts to the right in the direction of the arrow 178 andcloses, causing two actions.

First, the dump valve land 202 immediately equalizes pressure across thesimulated clutch piston 194, bypassing from the back of the piston 194,through the line 206 and bore core 204, thence into the differentialpressure chamber 80 to which the head of the piston 194 is exposed.Second, the valve sealing edge 182 seals off the drain bore core 180from the signal pressure chamber 82, and flow commences through the fillorifice 186 from the differential pressure chamber 80 into the lower, 20psi pressure S of the signal pressure chamber 82, to increase pressureS.

Immediately, hydraulic pressure on the load piston 164 will make itspresence felt so as to establish starting pressure for the desiredpressure rate of rise in the affected clutch, as can be understood fromFIG. 5.

RATE OF RISE, STARTING PRESSURE -- FIG. 5

With the valve parts in position as illustrated for this condition, theunopposed light piston spring 208 will start the simulated clutch fillpiston 194 in the direction of the arrow 196 to reset the piston againstthe stop pin 198. Also, the rising signal pressure S will aboutsimultaneously start the load piston 164 in the direction of theadjacent arrow on its load stroke.

At outset of movement of the load piston 164 on its load stroke,compression will increase in the relatively relaxed spring group 88,communicating itself to the modulating valve 58 and causing the valveland 90 to commence restricting outflow from the bore core 92 whichcarries pump line pressure P. There thus begins a linear rise ofpressure P and, proportionately, a linear rise of the pressures P1, P2,S, C, and PA.

Therefore, as the piston 194 in FIG. 5 completes its resetting strokeand the load piston 164 completes its load or control stroke, the spring104 maintains a continuous 30 psi differential of the linearly risingpressures C, P1, and P2 above signal pressure S, the differentialpressure across the timing orifice 186 remains constant at 30 psi, theflow rate through the orifice 186 remains constant throughout thepressure rate of rise, and the rate of movement of the piston 164 staysconstant throughout the linear pressure rise, which occurs at constantrate for each load or control stroke of the piston 164. That is to say,for a given stroke the rate of rise of pressure does not change althoughthe rate for one stroke may differ from other strokes for reasonshereinafter set forth.

LOAD PISTON -- FIG. 6

The referred to uniplanar four spaced control edges about the crown ofthe load piston 164 form part of eight consecutive outside portionsthereof, alternate ones of which are the same flats 214 defining thesealing control edges 170, and each remaining one of which is a land 216retaining its original cylindrical shape and being identical to theother three lands.

The four sealing edges 170 control the bore ports 172 constituting drainholes and, in practice, the drain holes as superimposed in FIG. 6subtend a central angle slightly in excess of the arcuate width,measured in a circumferential direction, of each of the lands 216.Irrespective therefore of the rotative position of the load piston 164in bore 34, not shown, one sealing edge 170 will have a bore port 172aligned in its path of reciprocation so that, by unblocking same, thesealing edge 170 concerned will determine the end of travel of the loadpiston 164 on each load stroke at the same point essentially.

Hydraulic balancing or centering grooves 218 are formed at spacedlocations in the exterior of the load piston 164 adjacent its open end.

RATE OF RISE CURVES -- FIG. 7

Without provision for my novel arrangement just described, clutchpressure at the end of fill can be substantially high due to incompleterecycling of the load piston, not shown, as illustrated by the brokenline rise curve 220 in this figure. That is to say, the end of fillpoint 222 on the curve 220 represents a residual 100 psi pressure, andthe modulated rate of rise will thus start off too soon to effect clutchengagement properly. Under my novel arrangement, however, the loadpiston is ready for a complete control stroke, at the point immediatelyafter clutch fill when the dump valve shifts to the right and thesimulated clutch piston starts resetting movement back to its startingposition, and the rate of rise proceeds in the desired way along thesolid line rise curve 224. The end of fill point 226 on the curve 224represents the desired 60 psi.

While the end of fill point is critical insofar as pressure isconcerned, the shorter rate of rise interval I1 is not in and of itselfundesirable; that is to say, the desired rate of rise interval I2indicated in FIG. 7 may be effectively shortened in a manner now to bedescribed, without failing to effect proper clutch engagement.

SHIFT IN SECOND GEAR -- FIGS. 7, 1, 2

In FIG. 7, the pressure trace will desirably have a steeper straightslope than shown by the curve 224 when a direction shift is made withthe transmission 10, not shown, in second gear. That is, in the higherspeed gear compared with first gear, a clutch change is not felt soabruptly; hence the clutch can go into engagement smoothly at arelatively larger constant rate of rise of pressure, and the interval I2will consequently be shorter.

In FIG. 1, the speed valve spool 48 in the way described has the speed 2position wherein the spool land 120 uncovers the mouth of the firstauxiliary passage 122 which is in reality an orifice. Such orificeprovides a second means of connection to the signal pressure chamber 82,supplementing the timing orifice flow described already as the firstmeans of connection to the signal pressure chamber 82.

In FIG. 2, the orifice formed by the first auxiliary passage 122communicates restricted flow through a gallery into a bore core 228,thus feeding the signal pressure chamber 82 and establishing a newlarger fixed rate of flow whereby the load piston 164 moves on loadstroke at a faster constant rate, for a correspondingly shorter periodof linear rate of pressure rise of both the signal pressure S and thevalve modulated first output pressure P1. So the rate of rise intervalI2 earlier described will be shorter but will cover the same full rangeof pressure, namely, from 60 psi as previously to 300 psi as previously.

SHIFT IN THIRD GEAR -- FIG. 2

When a shift is made with the transmission 10, not shown, in third gear,the subsequent rate of rise in pressure following fill will beestablished not only as described, by the first and second means ofconnection to the signal pressure chamber 82, but also by a third meansof connection consisting of the second auxiliary passage 124 which ismore or less unrestricted and which communicates essentially the fullpressure p1 through a gallery and into the bore core 228 which feeds thesignal pressure chamber 82. Although the end points of the rate of risecurve 224, not shown, have the same pressure ordinates at start andfinish, the slope is made much steeper and the constant rate of pressurerise is an appreciably larger figure. In other words, a shift when speed3 is involved can be made both rapidly and smoothly, albeit in theshortest rate of rise interval I2.

SPEED CHANGE IN SAME RANGE -- FIG. 1

Speed changes can be made from among the selected ones of the piston andcylinder units 1, 2, or 3 without disturbing the direction valve spool54, which can be left remaining in the forward position F, for example,as shown in FIG. 1.

Hence, the clutch filling process will involve only the selected speedclutch, and the clutch F will remain filled during the change speed.

SHIFT CYCLE PRESSURE CURVES -- FIG. 8

The solid line curve 230 represents the pressure trace for valve outputP1 and also valve output pressure P2 during a full cycle. The brokenline curve 232 represents the signal pressure S trace for the samecycle.

Following the pressure drop of both pressures at the outset of a shift,represented as essentially vertical straight lines at the extreme left,the simulated clutch fill piston 194, not shown, insures an approximate30 psi differential of the pressure P1 over the signal pressure S duringthe immediately ensuing fill interval F1.

Following fill, the sharp 10 psi pressure rise reflected at 234 in thesolid line curve 230 and reflected at 236 in the broken line curve 232is due to the sudden drop in flow upon filling of the clutch involved.That is, both pressures rise by about the amount of pressure rise acrossfill orifice 32, not shown, which no longer will generate anyappreciable drop thereacross.

The major portions of the curves 230 and 232 representing the modulatedlinear rates of rise of pressure and also those horizontal portionsrepresenting the equilibrium time E1 at full clutch pressure show aconstant differential of about 30 psi between the pressures P1 and S dueto the equivalent 30 psi mechanical compression residual in themodulation valve spring 104, FIG. 2.

SIMULTANEOUS SHIFT -- FIG. 8

In a shift requiring that the transmission go from a condition of, forinstance, R1 to F2, both the speed spool 48 and the direction spool 54,not shown, are newly positioned and newly detented in their respectivenew positions. The piston and cylinder unit F and also the piston andcylinder unit 2 require filling, so that the normally rather short filltime F will appear on the pressure trace as just about twice as long aninterval as the previous fill time F1 discussed in connection with FIG.8. Otherwise, the rate of rise modulation curves will appear the sameand both clutch engagements will occur in the desired way.

It will be apparent from the foregoing that my novel arrangement makesthe scheduling function independent of the variables of the system suchas line resistance, pressure drop, and clutch piston displacement. Sothe starting rise pressure will always be at a reduced level in thescheduling cycle and smooth clutch engagement will be assured. Rightafter clutch fill every time, the dump valve shifts rightwardly as shownin the drawings into fully closed position, and the simulated clutchpiston resets rightwardly to its starting position as viewed in thedrawings, already for the next shift. In effect the piston 194 locatedinside sleeve 188 within the dump valve cavity, FIG. 5, is like a smallclutch piston being subjected to an equal or at least an equivalentpressure during clutch fill as the clutch of the selected group orclutches of the selected groups are being likewise subjected. Thereforedespite its relative hydraulic remoteness to the latter, the rate ofrise valve assembly in housing 26 essentially knows the actual clutchpressure PA because PA is artificially approximated close-by by cavitypressure C in the differential chamber 80.

Variations within the spirit and scope of the invention described areequally comprehended by the foregoing description

What is claimed is:
 1. For use in a clutch controlled vehicle havingactivatable brake apply means for the vehicle brakes, a rate of risehydraulic system having a connection to individual lines of apiston-type, transmission-clutch group, wherein the fluid output of thesystem undergoes pressure loss to an actual clutch fill pressure inorder to pass from said connection through said individual lines toreach a selected clutch piston, said hydraulic system comprising:aclutch pressure modulating valve and signal pressure control means bothreciprocally mounted and in opposite ends of a bore formed by a valvehousing, said clutch pressure modulating valve being arranged to affordflow of the system fluid output to said connection, out of pumped fluidsupplied thereto from a pump source; said signal pressure control meanscomprising a dump valve member reciprocable toward and away from theadjacent end of the bore, and a differential pressure chamber definedbetween and by the dump valve member and said bore end and receivingsystem-output-fluid from said connection; said dump valve membercooperating with modulator loading means in said bore to define a signalpressure chamber, and said dump valve member providing a fluid output;means of connection from the dump valve member utilizing said dump valvefluid output to supply rising signal fluid pressure to the fluid insidethe signal pressure chamber; and neutralizer means and a selector valvemember disposed in series in said housing in that order at saidconnection; said neutralizer means delivering system fluid output to theselector valve member and responsive to activation of said vehicle brakeapply means to withhold system fluid output from the selector valvemember; said selector valve member having spool valve portions effectivein progressive selector valve positions for cooperating with saidindividual lines to direct, to selected ones of the clutch pistons, thesystem fluid output delivered by said neutralizer means.
 2. For use in apower-shift vehicle having activatable brake apply means for the vehiclebrakes: a rate of rise hydraulic system having a connection (conductingpressures P₁, P₂, P_(A)) to individual lines of a plurality of fluidoperated piston type, power-shift, friction engaging drive devices(F-R), wherein the fluid output of the system undergoes pressure loss toan actual fill pressure of each device in order to pass from saidconnection through said individual lines to reach a selected fluidoperated piston, said hydraulic system comprising:a pressure modulatingvalve (58) and signal pressure control means both reciprocally mountedand in opposite ends of a bore formed by a valve housing, said pressuremodulating valve being arranged to afford flow of the system fluidoutput to said connection, out of pumped fluid supplied thereto from apump source; said signal pressure control means comprising a dump valvemember reciprocal toward and away from the adjacent end of the bore, anda differential pressure chamber defined between and by the dump valvemember and said bore end and receiving system-output-fluid from saidconnection; said dump valve member cooperating with modulator loadingmeans in said bore to define a signal pressure chamber; first (186) andsecond (122, 124) means of connection from the dump valve member andselector valve member, respectively, utilizing system fluid outputtherefrom to supply rising signal fluid pressure to the fluid inside thesignal pressure chamber; and neutralizer means (44) and a selector valvemember (54) disposed in series in that order at said connection; saidneutralizer means delivering system fluid output to the selector valvemember and responsive to activation of said vehicle brake apply means towithhold system fluid output from the selector valve member; saidselector valve member having spool valve portions effective inprogressive selector valve positions for cooperating with saidindividual lines to direct, to selected ones of the fluid operatedpistons, the system fluid output delivered by said neutralizer means. 3.For use in a power-shift vehicle having activatable brake apply meansfor the vehicle brakes: a rate of rise hydraulic system having aconnection (conducting pressures P₁, P₂, P_(A)) to individual lines of aplurality of fluid operated piston type, power-shift, friction engagingdrive devices (F-R), wherein the fluid output of the system undergoespressure loss to an actual fill pressure of each device in order to passfrom said connection through said individual lines to reach a selectedfluid operated piston, said hydraulic system comprising:a pressuremodulating valve (58) and signal pressure control means oppositelydisposed and both reciprocally mounted in a bore formed by a valvehousing, with the pressure modulating valve in a first end and thesignal pressure control means in a second end of the bore; a load pistonin the bore intermediate its first and second ends, and arranged withthe signal pressure control means to form a signal pressure chambertherebetween in the bore; spring means arranged for loading interactionbetween the load piston and said valve; said signal pressure controlmeans including a differential pressure chamber, with a simulated clutchfill piston therein affording an enlargement of volume of thedifferential pressure chamber during actual clutch fill; means formingpaths leading respectively: from the valve assembly fluid output throughthe differential pressure chamber, thence through first means (186) inthe signal pressure control means to the signal pressure chamber forcausing a control stroke of the load piston against the spring means;and from the signal pressure chamber thence through second means (174)in the signal pressure control means to drain, during actual clutch filland corresponding enlargement of the differential pressure chamber bythe simulated clutch fill piston therein; and neutralizer means (44) anda selector valve member (54) disposed in series in that order at saidconnection; said neutralizer means delivering system fluid output to theselector valve member and responsive to activation of said vehicle brakeapply means to withhold system fluid output from the selector valvemember; said selector valve member having spool valve portions effectivein progressive selector valve positions for cooperating with saidindividual lines to direct, to selected ones of the fluid operatedpistons, the system fluid output delivered by said neutralizer means. 4.For use in a power-shift vehicle having activatable brake apply meansfor the vehicle brakes: a rate of rise hydraulic system having aconnection (conducting pressures P₁, P₂, P_(A)) to individual lines of aplurality of fluid operated piston type, power-shift, friction engagingdrive devices (F-R), wherein the fluid output of the system undergoespressure loss to an actual fill pressure of each device in order to passfrom said connection through said individual lines to reach a selectedfluid operated piston, said hydraulic system comprising:a pressuremodulated valve (58) and signal pressure control means oppositelydisposed and both reciprocally mounted in a bore formed by a valvehousing, with the pressure modulating valve in a first end and thesignal pressure control means in a second end of the bore, said valvebeing arranged to afford flow of the valve assembly fluid output, out ofpumped fluid supplied thereto from a pump source; a load piston in thebore intermediate its first and second ends, and arranged with thesignal pressure control means to form a signal pressure chambertherebetween in the bore; spring means, arranged for loading interactionbetween the load piston and said valve; said signal pressure controlmeans having a differential pressure chamber, and having first means totransfer timing fluid from the differential pressure chamber to thesignal pressure chamber for causing a control stroke of the load pistonagainst the spring means, and second means to vent signal pressure toreduced value to reset the load piston during actual clutch fill, saiddifferential pressure chamber being included in said signal pressurecontrol means and with a simulated clutch fill piston therein movable toa chamber-enlarging position affording an enlargement of volume of thedifferential pressure chamber during actual clutch fill; admission means(212) connected between the valve assembly fluid output and differentialpressure chamber whereby, during actual clutch fill and correspondingenlargement of the latter by the simulated clutch fill piston therein,to admit the valve assembly output fluid to the differential pressurechamber at reduced pressure equivalent to signal pressure, effectivelyequalizing pressure across the signal pressure control means andenabling the load piston to fully reset against the equivalent of actualclutch fill pressure; and neutralizer means (44) and a selector valvemember (54) disposed in series in that order at said connection; saidneutralizer means delivering system fluid output to the selector valvemember and responsive to activation of said vehicle brake apply means towithhold system fluid output from the selector valve member; saidselector valve member having spool valve portions effective inprogressive selector valve positions for cooperating with saidindividual lines to direct, to selected ones of the fluid operatedpistons, the system fluid output delivered by said neutralizer means.